Are slats shy ?

[Crumpp]

You presented a value from flaps extended polars, as you say the stall happens at ~17.5°, which is only the case with flaps extended. Good to know it wasn't intentional.

Figure it out yourself. You have no clue how to read a polar and I am not going to teach you.

AoA the slats open at.

A little basic knowledge and anyone can tell you are "out der FLAPPIN" as we used to say in the Army when somebody was completely wrong. In this case, it is quite ironic you are FLAPPIN over flaps!!



The effect of trailing edge flaps is to increase the camber of the wing.

Flaps change the airfoil pressure distribution, increasing the camber of the airfoil and allowing more of the lift to be carried over the rear portion of the section.

What is the effect of a camber increase on a lift polar??

It shifts the whole polar to the right! That means it LOWERS our Angle of Attack!! You cannot have the same Angle of Attack flaps up as you do flaps down....

Check out figure 5:

Figure 5. DC-9-30 CL vs. Flap Deflection and Angle-of-Attack

http://adg.stanford.edu/aa241/highli...liftintro.html

It is not physically possible with TE flaps to have the same general CLmax presented by the RAE in clean configuration with a polar with the TE flaps down at the same Angle of Attack.

Which incidentally also matches the 2D data from the NACA family of airfoils.

BTW you can see the data point Mtt plotted for the plain airfoil and for the slats on the polar. The Bf-109 did not have full length LE slats so it did not get a dramatic CLmax increase.

[JtD]

Originally Posted by Crumpp

The designs for the radiator flaps of the F series were tested as well during this investigation. In fact the aircraft, for those test's the aircraft was fitted with an F series cowling (intake), wheel well covers, and the various radiator flap designs being considered.

That makes a little bit of sense, as the chart explicitly states "Spreizklappen innen" - "slotted flaps inwards". Which probably means they only changed the part around the radiator.

Originally Posted by Crumpp

What is the effect of a camber increase on a lift polar??

It shifts the whole polar to the right! That means it LOWERS our Angle of Attack!! You cannot have the same Angle of Attack flaps up as you do flaps down....

I'd think they move to the left, i.e. proving more lift for the same AoA...but I don't see how the trailing edge flaps suddenly became the issue.

BTW you can see the data point Mtt plotted for the plain airfoil and for the slats on the polar. The Bf-109 did not have full length LE slats so it did not get a dramatic CLmax increase.

That's interesting and impossible to know from just looking at the chart - these dots carry no designation and could be anything, in particular as the same dots cannot be distinguished in the flaps extended polars. So thanks for telling.

[Crumpp]

but I don't see how the trailing edge flaps suddenly became the issue.

Of course not....that would mean you spouted off without knowing the context or details, posting something to discredit whatever I said.

I'd think they move to the left,

It does move to the left when TE flaps deploy. A camber change shifts the lift curve reducing the AoA CLmax for the airfoil occurs.

In this case though you claimed that the top polars were different designs of TE flaps deployed and their effect. They were different designs of radiator flaps as I stated in my first reply of too many to you.

Therefore, the curve in question on the bottom would be shifted to the right if that was the case. You started posting about the language used on the polar out of context and without the details.

JtD your focus is never on the topic at hand. It is only to discredit anything I say in any way that you can.

I have nothing further on this topic or any other topic for you. You can work whatever angle you dream up to claw at this conversation but I wish you good luck in your life.

The good thing is that by this way you hve an independent behavior for both slat that can result in asymmetric deployment

For the readers, asymmetric deployment is normal. As the slat works as required, it does not effect the flight of the aircraft at all compared to symmetrical deployment.

It only becomes a problem when if the slats experience a mechanical malfunction and one slat cannot meet the force required.

[TomcatViP]

Originally Posted by IvanK

To be pedantic slats are not speed dependant and work solely as a function of AOA though in 1g flight AOA and IAS are intrinsicly linked.
Not having the ball centred could easily result in different AOA on each wing and hence result in asymmetric slat deployment ... as can aileron input.

The Slat animation in CLOD at the moment is imo out of whack with what they should be doing. They should be coming out and staying out a lot earlier than they are at present. There is some discussion with the Devs on this going on using RAE test reports to come up with better more realistic operation. Not exactly sure when will actually see this.

The RAE data has 1G IAS (since they wernt recording AOA) slat deployment values for both the 109 and 110. These values can be used to extrapolate values for slat deployment at other G values. The essence being that AOA for slat deployment will always be the same, whilst IAS v G will change in a similar way to accelerated stall speeds v 1g stall speeds ie. Vstall X SQR G

Hi IvanK,

I hve been thinking at the solution you wrote over the night and I hve some doubt of the solution proposed: V_SlatOut = VstallxSQR(G)

At first I understand that this is similar to old IL2 and thus is a satisfactory solution for all. However my point here is that it cld be improved.

Slat deployment on the 109 was governed by the air pressure on the leading edge (LE) and the hinged mechanism weight and frictions forces.

a. Frictions forces are cte (K)
b. Weight effect is dependent on G (P=mg)
c. Dyn Pressue acting on the slat is a function of the speed of the plane (V) and the AoA (alpha) with Pdyn = 0.5roV²S*cos(alpha)

Hence we have V_SlatOut = f(G, Pdyn) + K

At 1G, the speed being known, as is the AoA we have the resulting value of the Weight and friction of the mechanism given that we make the calculation of the projected surface of the slat

We can now choose to consider the friction of the mechanism negligible given tht the slat were known to be retractable only by the application of one finger (and much attention were required to keep the slat close on the ground to protect the mechanism from ingesting dust, sand and small objects).

So basically we will hve V_SlatOut = f(G, Pdyn) tht result in the programmed law :

If V<= V_Stall*SQR(G) and If Pdyn>=mg (m being the resulting balancing mass calculated at the 1G condition) Then Slats Out.

The good thing is that by this way you hve an independent behaviour for both slat that can result in asymmetric deployment

Pls note tht the Weight I am talking abt is not really a mass per G. It's the seen mass by the system combining all efforts in the mechanism that result in the deployment of the slat minus the friction. I am pulling away the frictions forces as they are not dependent of the G and are basically negligible if the system is functioning optimally.

EDIT:

Sry Crumpp I did delete my post as I needed to check my info. Here it is right as before.

I checked the deployment principles here http://109lair.hobbyvista.com/index1024.htm

[David198502]

just a small vid i just made to spice this interesting thread up..

http://www.youtube.com/watch?v=cewk7t_gN-w

[JtD]

Originally Posted by Crumpp

It does move to the left when TE flaps deploy.

Then why do you say the opposite, first?

In this case though you claimed that the top polars were different designs of TE flaps deployed and their effect. They were different designs of radiator flaps as I stated...

The Messerschmitt engineers referred to them as trailing edge flaps, but since the radiator flap was part of the trailing edge flap, I don't even understand what point you're trying to make now?

Therefore, the curve in question on the bottom would be shifted to the right if that was the case.

The curve on the bottom would shift to the right if wing camber increased? It wouldn't. In case I misread you, can you please post a little bit more coherent (leaving out the "u suck I rule" stuff would help)?

You could still explain how you see that the slats deploy within the 2.5° between 8 and 11.5° AoA as you said. From where I am standing, it is not on the chart.

[Crumpp]

Sry Crumpp I did delete my post as I needed to check my info. Here it is right as before.

No problem and I wasn't trying to correct you. Sorry if it came across that way.

Appreciate the insight!

No problem at all. I hope it helps.

just a small vid i just made to spice this interesting thread up..

Thanks for posting that.

Can you make one and stall the aircraft in 1G level flight and then stall it left/right in a level turn please? Also deploy the slats in turn by pulling the stick back and retract them by releasing it like I did on my aircraft to see what level of control you have.

My practical experience with 109 slats (actually, Buchon, so late version and no, I haven't flown them - lol) is that on the ground they're very definitely either up or down. The mechanism doesn't seem to hint at any kind of balance anywhere in between, it's all up or all down. They do seem rather secure in the up position while on ground but I could imagine with a plane bumping around on the grass during takeoff they would likely pop down, but there would be contributing air loads going on as well, obviously.

It also struck me while I was fiddling with them that it might take a little less AoA to pop them back in that what popped them out. If so, that would reduce the chance of having them banging back and forth if one happened to be riding the magic AoA.


--- Let me know when I can groundloop a 109 (or anything else, for that matter - lol) in game. ---

[CaptainDoggles]

Originally Posted by cheesehawk

I just don't imagine myself ever in a dogfight thinking, how can I make this slat partially deploy!

That's the beauty of the design. They work automatically, allowing the pilot to maintain control at higher angles of attack without devoting mental effort to it.

[TomcatViP]

Originally Posted by zipper

My practical experience with 109 slats (actually, Buchon, so late version and no, I haven't flown them - lol) is that on the ground they're very definitely either up or down. The mechanism doesn't seem to hint at any kind of balance anywhere in between, it's all up or all down. They do seem rather secure in the up position while on ground but I could imagine with a plane bumping around on the grass during takeoff they would likely pop down, but there would be contributing air loads going on as well, obviously.

It also struck me while I was fiddling with them that it might take a little less AoA to pop them back in that what popped them out. If so, that would reduce the chance of having them banging back and forth if one happened to be riding the magic AoA.


--- Let me know when I can groundloop a 109 (or anything else, for that matter - lol) in game. ---

Thx for sharing Zip.

I understand here that friction wld be negligible as supposed.